CVE-2026-20079: Cisco Firewall Management Center Authentication Bypass Using an Alternate Path or Channel Vulnerability

What it is

Cisco Secure Firewall Management Center (FMC) Software and Cisco Security Cloud Control (SCC) Firewall Management contain an authentication Bypass using an alternate path or channel vulnerability that could allow an unauthenticated, remote attacker to bypass authentication and execute script files on an affected device to obtain root access to the underlying operating system.

What to do

Treat this as urgent. Identify every affected system, starting with anything internet-facing, and apply the vendor fix or mitigation within days. If you cannot patch quickly, isolate or disable the affected service and watch for signs of compromise.

Priority

Act now: Patch or mitigate internet-facing systems within days.

Severity (CVSS)

10 critical

CISA assessment (SSVC)

actively exploited; attackers can automate it at scale; total control of the affected system

Exploit probability (EPSS, 30 days)

88%, in the top 1% of all CVEs

Added to CISA KEV

9 September 2026

CISA fix-by date

12 September 2026 (US federal agencies; a sensible deadline for everyone)

Ransomware use

Not known

Weakness

CWE-288

References

• NIST NVD entry
• CISA KEV entry
• sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-o
• seclists.org/fulldisclosure/2026/Aug/80
• blog.talosintelligence.com/fmc-ongoing-exploitation/
• www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2026-20079

Sources: CISA Known Exploited Vulnerabilities · FIRST Exploit Prediction Scoring System (EPSS) · NIST National Vulnerability Database · CISA Vulnrichment (SSVC), via the CVE Program. This product uses data from the NVD API but is not endorsed or certified by the NVD. Summaries are machine-written from CISA’s description; treat the vendor’s advisory as the authority for fixes.